1. Field of the Invention
The present invention relates generally to meters, and particularly to a meter having a dial plate illuminated from back by a light source and a light transmitting plate. The present invention is suitably applied to a meter disposed on an instrumental panel of a vehicle.
2. Related Art
JP-A-9-21655 discloses an illumination structure for a meter used as a speedometer of a vehicle. In the meter, a light transmitting plate is layered at a rear side of a dial plate, and plural light sources are disposed below the light transmitting plate. Light from the light sources is introduced into the light transmitting plate, and is reflected by the light transmitting plate toward the dial plate. As a result, translucent indication marks and graduations formed on the dial plate are illuminated from back. Light from the light sources is also introduced into a light transmitting pointer disposed on the dial plate, and illuminates the pointer. The light sources are disposed around a shaft of the pointer, and the light transmitting plate has a shaft hole through which the shaft of the pointer passes. Light from the light sources is introduced into the light transmitting plate from the shaft hole.
However, since the light transmitting plate around the shaft hole is formed flat, incidence efficiency of light from the light sources into the light transmitting plate is poor. Especially, when the light sources are light-emitting diodes (LEDs), a large number of the LEDs may need to be used to increase amount of light introduced into the light transmitting plate, because the LED is generally smaller in size and emission area than a lamp. As a result, the number of the light sources may be increased, thereby increasing manufacturing cost of the meter.